This invention relates generally to apparatus for removing noxious contaminants from aqueous systems, and more specifically relates to filtration devices and methods for removing both oily and slightly soluble organic compounds from such aqueous systems. The invention is particularly applicable to the removal of such contaminants from drainage water, such as collected rainwater.
Increasing public awareness and concern regarding the effects on human and animal life of contamination of water sources, has led in recent years to the focusing of attention on contamination of drainage water. Simple rainstorms can generate torrents of water on city streets, and at paved and unpaved parking and other facilities, which water as it sweeps over these surfaces and into drains and catch basins, carries with it large quantities of oils, pernicious chemicals and the like, not to mention various solid and semisolid debris. A graphic picture of such events can be visualized by considering the resulting drainage when a rainstorm sweeps water across and through a large truck stop. The parking surfaces at such a facility are commonly stained with a variety of oily hydrocarbons, antifreeze, hydraulic fluids and the like. The resulting drainage of the rainwater carries these pernicious materials to groundwater tables, or to rivers, lakes and the like, all of which are often the source of public drinking waters. Aside from the addition of water insolubles such as oils and greases, this leads to the water sources being contaminated with pernicious slightly soluble organic compounds such as benzene, toluene, xylene, halogenated hydrocarbons, ethoxylated glycols, etc. These noxious contaminants are among the more difficult compounds to remove from water, and indeed most are carcinogenic.
Various devices and apparatus have been long known and used for removing or separating certain contaminants and debris from drainage water. An excellent example of a modern such device to which the present invention is applicable is disclosed in U.S. Pat. No. 5,759,415, the entire disclosure of which is hereby incorporated by reference. The said device has a tank defining a chamber with an inlet and a pair of vertically spaced outlets. A bulkhead with openings is spaced opposite the inlet and extends from the base of the chamber. A baffle is located between the bulkhead and the outlets and extends from the top of the chamber to near the bottom. An orifice plate or plates is adjustable mounted in series with the outlets and controls the rate of flow therethrough. The system is seen as having four sections, namely a non-floating particulate containment chamber; a floating particulate containment chamber; a flow control chamber; and an outlet chamber.
This prior art device is illustrated in FIGS. 1 through 3F, and includes a tank 12, an inlet pipe 14, a bulkhead 16, baffle 18, removable cover 20, orifice plate 22, and weir plate 23, low-level outlet 24, and high-level outlet 26, openings 28 and 29 in bulkhead 16, and outlet pipe 30. As seen in FIG. 2, the bulkhead 16 and the wall of the tank 12 make a generally ovate or circular non-floating particulate containment chamber 31 and the inlet pipe is axially offset from the center of this chamber. The water enters through inlet pipe 14 and, due to the offset of the pipe and chamber shape, a swirling motion is imparted to the flow. The non-floatable particulate entrapped therein is contained by bulkhead 16. The bulkhead openings 28 and 29 allow passage of water. The bulkhead is constructed such that the floatable particulate flows through the bulkhead. Much of the floatable particulate is then contained by the baffle 18. The orifice plate 22, through which the low level water exits, controls the low level water flow. The weir plate 23, through which the high level water exits controls the high level water flow. The arrows in FIG. 2 show the drainage path taken by the rainwater through the subject invention. FIGS. 3A to 3F show the device during different stages of operation. The phantom line in FIG. 3A indicates the water level 50 before or after a drainage event when there is little or no drainage flow. The phantom line in FIG. 3B indicates the water level 50 during the initial phase of operation with non-floatable particulate being retained by bulkhead 16 and floatable particulate by baffle 18. The phantom line in FIG. 3C indicates the water level 50 during the transitional phase of operation as the volume of flow increases. The phantom line in FIG. 3D indicates the water level 50 during full capacity phase operation. The phantom line in FIG. 3E indicates the water level 50 which decreases during the phase in which water ceases to enter the invention 10. The phantom line in FIG. 3F indicates the water level 50 after all drainage has ceased, and the non-floating particulate containment chamber 31 has been cleaned.
In use, water drainage possibly mixed with sewage, enters the tank 12 through the inlet 14, resulting in a swirling motion being imparted thereto. Initial drainage at very low levels begins through opening 29. As flow levels increase the water level rises behind the bulkhead 16 until it is higher than the crest of opening 28 at which point the water level rises in the rest of the tank 12. Oil and other floating particulate, which are mixed in the water rise along with the overall water level. The overall water level rises as the water flows through the openings 28 and 29 and exits through the low-level outlet 24 at the rate controlled by the orifice plate 22. The orifice plate 22 is slightly higher than the opening 29 thereby allowing skimming of the non-floating particulate into the containment chamber during cleaning. The overall water level rises because the inlet flow rate exceeds the outlet flow rate. This is referred to as the initial phase, as shown in FIG. 3B. During the next phase, referred to as the transition phase, as shown in FIG. 3C, the vertical separation distance between the floating particulate and the bottom of the baffle 18 increases. The water level rises to the level of the high level outlet 26, as shown in FIG. 3D. The rate of flow of the exiting water is increasing slightly as the water level is increasing but is still controlled by the orifice plate 22. This continues until the water level rises above the opening in the weir plate 23 at the high level outlet 26. At this point the flow rate through the tank 12 begins to increase significantly.
During the next phase, referred to as the full capacity phase, as shown in FIG. 3D, the high outlet 26 is controlled by plate 23 which is designed to transfer as much water as the outlet pipe 30 can discharge. This continues until the rate at which the water is introduced through the inlet 14 decreases to the point where the water level drops below the level of the high-level outlet 26. The remaining water in the tank 12 is discharged at a rate determined by the orifice plate 22. Eventually the water level drops to the invert elevation of the orifice plate 22 which covers the low level outlet 24 as shown in FIG. 3E. Now the point has been reached where there is no flow through the tank 12. The overall low water level as shown in FIG. 3E permits an easy inspection. The level of particulate accumulation can be determined for example by removing covers 20 to see if there is enough accumulated floating and non-floating particulate to necessitate the cleaning to the tank 12.
For purposes of the present specification apparatus of the foregoing type which are used to separate floating and non-floating particulates from drainage water, shall be referred to as xe2x80x9cdrainage separating tanksxe2x80x9d. While drainage separating tanks of the type illustrated are indeed useful for separating sediment and other solid and semisolid materials from drainage water, they are of limited value in removing insoluble oils and the like, and are of essentially no value in removing slightly soluble organics of the pernicious types which have been discussed above.
Now in accordance with the present invention, it has been found that by incorporating certain fluid-previous filtration materials into or at drainage water accessible portions of drainage separating tanks, both oily water insoluble contaminants (e.g. oil spills, asphalt spills and the like), as well as slightly soluble organics such as benzene, toluene, xylene, halogenated hydrocarbons, ethoxylated glycols, etc., may be readily removed from the drainage water, leaving a safe water product for discharge from the separating tank. The filtration materials used incorporate the compositions disclosed in the present inventor""s U.S. Pat. Nos. 5,437,793; 5,698,139; and 5,837,146, and in said inventor""s copending patent application Ser. No. 08/856,263 (all of which disclosures are hereby incorporated by reference). These compositions have extremely strong affinities for all of the aforementioned contaminants in water, and when aqueous streams or volumes containing these noxious contaminants are passed through or otherwise contacted with filtration media incorporating these inventive compositions, the contaminants are immobilized at the media, as a result of which concentration levels of the contaminants in the remaining water may be reduced to very low values, in some instances below detectable limits.
Filter configurations incorporating the said compositions (hereinafter referred to as xe2x80x9cabsorbent compositionsxe2x80x9d) may be based on various water permeable substrates, such as shredded, spun or otherwise configured polypropylene or shredded or spun cellulose, which substrates are infused or otherwise treated with the absorbent compositions, which are then cured. These substrates may then be packed or otherwise disposed in selected portions of the containment vessel; or can be formed into cured and infused bag filters which can be emplaced in the vessel. Similarly the said absorbent compositions can be incorporated into or upon other filtering substrates and media, such as paper, including compressed pulp materials, particulate porous foamed plastics, mineral particulates such as perlite and vermiculite, and particulate, fibrous or porous ceramic or porous (e.g. sintered) metal substrates and media.
It should be appreciated that the use herein of the term xe2x80x9cabsorbent compositionxe2x80x9d is one of convenience for identifying the compositions of my aforementioned patents and patent applications. The mechanism by which the absorbent compositions remove oils asphalts and the like appears to be one akin to coagulation as is discussed in the aforementioned patents. The specific mechanism by which the noxious slightly soluble contaminants are removed from aqueous streams by conjunctive use of the xe2x80x9cabsorbent compositionsxe2x80x9d is not completely understood, and could include attachment and/or fixation of such contaminants by mechanisms which technically involve various physical and/or chemical interactions. The term xe2x80x9cabsorbentxe2x80x9d as used herein is intended to encompass all of these possible mechanisms.